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Unformatted text preview: 72 Your Turn... The exothermic decomposition of peroxide was determined to occur via two separate steps in which the first step is the rate determining step. Which of the following three potential energy diagrams best summarizes these findings. A.
R Energy Energy B.
R P reaction coordinate C.
R Energy P reaction coordinate P reaction coordinate CHM1311 Chemical Kinetics 73 CATALYSIS Catalysts speed up reactions by altering the mechanism to lower the activation energy barrier. Catalyst has no effect on the reactants and products, enthalpy does not change! It does not make more products!! It is purely kinetic, not thermodynamic CHM1311 Chemical Kinetics 74 Catalysis and Activation Energy Example: MnO2 catalyzed decomposition of H2O2 2 H2O2 2 H2O + O2 Uncatalyzed reaction Catalyzed reaction CHM1311 Chemical Kinetics 75 Catalysis the catalyst must not be consumed in the reaction the catalyst accelerates the reaction by providing an alternate pathway for the reaction usually, the new mechanism is faster because the activation energy barrier is lowered CHM1311 Chemical Kinetics 76 Catalysis the catalyst does not affect the difference in energy between the reactants and products thus it does not affect the final equilibrium position the catalyst also increases the rate of the reverse reaction gets to equilibrium faster!!
!Ea k = Ae RT Ea k rate CHM1311 Chemical Kinetics 77 Chapter 14: Key Concepts 1. 2. 3. 4. 5. 6. 7. Reaction rate expression Measuring reaction rates The rate law Zero, first, and second order reactions Reaction profiles and activation energy The Arrhenius equation Catalysis (*no enzyme catalysis) CHM1311 Chemical Kinetics 78 Chapter 14: Suggested Problems 5, 7, 9, 11, 17, 19, 21, 33, 35, 39, 43, 47, 51, 55, 59, 67, 69, 78, 94 CHM1311 Chemical Kinetics 79...
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This note was uploaded on 01/16/2013 for the course CHM 1311 taught by Professor Mayer during the Fall '08 term at University of Ottawa.
- Fall '08